88 ANGIOSPERMAE—DICOTYLEDONES 



563. Trachelospermum L. 



1864. T. jasminoides Lem. — Hildebrand states that the flower mechanism 

 of this species is the same as that of Vinca. 



564. Tabemaemontana Plum. 



1865. T. echinata Aubl. — Fritz Muller says that this species is only fertile 

 with the pollen from other stocks (Bot. Ztg., Leipzig, xxviii, 1870, p. 274). 



565. Apocynum L. 



Flowers homogamous, with concealed nectar, secreted and stored in their bases. 



1866. A. androsaemifolitim L. (Ludwig, Bot. Centralbl., Cassel, viii, 1881, 

 pp. 184-5.) — Ludwig says that this species bears campanulate whitish flowers with 

 internal red streaks serving as nectar-guides, and five basal nectaries of which the 

 secretion possesses an unpleasant sweetish odour. The short filaments are beset 

 with hairs playing the part of nectar-covers. The five anthers make up a cone 

 surrounding the capitate end of the style. This is divided by a ring into upper and 

 lower parts, the latter serving as a stigma. The inner sides of the stamens, somewhat 

 above the centre of their length, are fused with this ring, so that a chamber is formed 

 into which the pollen falls without touching the stigma. The backs of the anthers 

 are thick angular woody plates, which prevent insects from gnawing away the upper part 

 of the stamens and style so as to make a more convenient way to the nectar. The 

 chinks between the anthers narrow above, and serve as clips to hold fast unbidden 

 guests. The actual pollinators (bees, and the larger hover-flies and Muscids) after 

 sucking nectar are obliged to withdraw their proboscis between the anthers, i. e. 

 through these clips, and it can only be freed by the exercise of considerable force. 

 During this withdrawal the proboscis passes over the stigma, and its sticky upper 

 edge through the pollen-chamber, from which it takes up some of the adhesive 

 granular pollen, to be transferred to the next flower visited. The smaller and weaker 

 insects, which are unable to penetrate the pollen-chamber and are therefore useless 

 guests, remain held fast by the clips to perish miserably. Among these Ludwig 

 observed numerous Muscids (Spilogaster carbonella Zel/., Scatophaga merdaria F., 

 Anthomyia pluvialis Z.), sometimes small Hymenoptera, and occasionally Lepi- 

 doptera. The presence of numerous dead flies (and proboscides and limbs of these) 

 in the flowers shows that there must be a large number of these unskilled visitors. 



Visitors. — Loew observed the following in the Berlin Botanic Garden. — 



A. Coleoptera. {a) CoccivelUdae -. i. Coccinella quattuordecimpunctata Z., 

 resting in the flowers. (U) NitiduUdae : 2. Meligethes sp., nect-lkg. in the bases of 

 the flowers, (c) Piinidae : 3. Anobium striatum 01., in the bases of the flowers. 

 B. Diptera. (a) Musadae : 4. Anthomyia sp., caught by the proboscis in the 

 flowers; 5. Onesia floralis Ji. D., do. {6) Syrphidae: 6. INIelanostoma mellina Z., 

 caught by the proboscis in the flowers ; 7. Platycheirus scutatus Mg., do. ; 8. Syritta 

 pipiens, Z., do. 



1867. A. cannabinum L. (= A. hypericifolium Aii^. (Ludwig, op. cit.) — 

 Ludwig describes this species as bearing much smaller, more inconspicuous, greenish 

 or yellowish-white flowers, devoid of nectar-guides, and possessing a still more 



